A retrievable secondary cyclonic separator, process column and method

Abstract

The application provides a fishing secondary cyclone separator, a process pipe column and a method, relates to the technical field of downhole oil-water separation, and the separator comprises, from bottom to top, a locking mechanism, a flow regulation water nozzle, a secondary oil production pipe and a secondary cyclone core in sequence, the locking mechanism is provided with a limiting structure and is used for cooperating with a downhole Y joint to be locked, the flow regulation water nozzle is used for adjusting the oil collection proportion of primary oil production and secondary oil production, the secondary cyclone core is used for carrying out secondary cyclone separation on the reinjection water after primary separation, and the separated oil-rich produced liquid enters the secondary oil production pipe. The process pipe column comprises the fishing secondary cyclone separator, the method adopts the process pipe column, and the application is used for improving the separation efficiency, ensuring that the downhole separation system is long-term effective and reliable in operation when the downhole produced liquid physical property parameters change and injection-production parameters are adjusted.

Description

Technical Field

[0001] This invention relates to the field of downhole oil-water separation technology, and in particular to a deployable two-stage cyclone separator, process tubing, and method. Background Technology

[0002] Currently, the problem of high water cut in oilfields is becoming increasingly serious, severely restricting stable production of oil fluids. Downhole oil-water separation technology can effectively solve the high water cut problem. Through downhole oil-water two-phase separation, high-oil-content produced fluids are lifted to the surface, while low-oil-content wastewater is reinjected into suitable downhole formations. This alleviates the burden of surface produced fluid treatment, reduces lifting energy consumption, and improves the economic benefits of oilfield development.

[0003] In recent years, downhole oil-water separation technology has been widely studied and applied. Among them, cyclone separators have become the mainstream technology for downhole oil-water separation due to their advantages such as compact structure, high separation efficiency and no moving parts.

[0004] However, single-stage hydrocyclones have high requirements for the oil properties of the produced fluid (such as density difference, viscosity, and oil content). When the water content of the downhole produced fluid increases further or its properties change, the separation efficiency of the single-stage separator decreases significantly, leading to excessive oil content in the reinjection water. This not only contaminates the injection layer but may also cause formation blockage, affecting the injection-production effect. This makes the well selection conditions for single-stage hydrocyclones quite stringent, limiting their application scope.

[0005] To improve separation efficiency, two or even more cyclone separators are sometimes used in series, that is, the first and second stage cyclone separators are fixedly installed in series inside the same outer tube and lowered into the well as a whole. However, this fixed series structure has the following problems: First, the two-stage separator is lowered as a single tubing section, which increases the complexity of the system and the difficulty of lowering it. This is especially true in environments with limited operating space and high construction costs, such as offshore oil fields, where the risk of construction operations increases significantly.

[0006] Secondly, the physical properties of the produced fluid in the well will change dynamically with the adjustment of injection and production parameters and the change of production time. The fixed structure of the two-stage separator cannot adjust the operating parameters according to the actual working conditions, resulting in unsatisfactory separation effect.

[0007] Therefore, there is an urgent need for a two-stage hydrocyclone separator, process tubing, and method that can be used to solve the above-mentioned technical problems. Summary of the Invention

[0008] The purpose of this invention is to provide a deployable two-stage cyclone separator, process tubing, and method to address the problems in existing technologies where the two-stage separator is run as a single unit, increasing system complexity and difficulty, especially in environments with limited operating space and high construction costs, such as offshore oil fields, significantly increasing operational risks. Furthermore, the invention addresses the issue that the physical properties of the produced fluids dynamically change with adjustments to injection and production parameters and production time, making it impossible for a fixed-structure two-stage separator to adjust operating parameters according to actual conditions, leading to unsatisfactory separation results. The preferred technical solutions provided by this invention offer numerous technical advantages, which are detailed below.

[0009] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a two-stage hydrocyclone separator capable of being retrieved, comprising, arranged sequentially from bottom to top: A locking mechanism, wherein the locking mechanism is provided with a limiting structure for engaging with a downhole Y-connector for locking; A flow control nozzle, which is used to adjust the oil collection ratio between the primary oil extraction stage and the secondary oil extraction stage; Secondary oil extraction tubing; The secondary cyclone core is used to perform secondary cyclone separation on the reinjected water after primary separation, and the separated oil-rich product enters the secondary oil extraction pipe.

[0010] Furthermore, it also includes a check valve, which is located upstream of the secondary oil intake pipe to prevent the backflow of the separated rich oil product.

[0011] Furthermore, the limiting mechanism includes a locking boss, which is used to engage with the locking groove of the Y-joint to prevent rotational locking.

[0012] Furthermore, the limiting mechanism also includes a first positioning step, which is used to engage with the second positioning step of the Y-joint for locking, thereby axially positioning.

[0013] Secondly, the present invention provides a downhole oil-water separation process string for a deployable two-stage cyclone separator, comprising the aforementioned deployable two-stage cyclone separator, an outer casing, and, disposed inside the casing, sequentially connected from bottom to top, a perforated pipe, an insertion seal, a central tubing, a positioning seal, a bridge-type channel, a Y-joint, a lifting tubing, a cable packer, and a downhole safety valve, wherein: The lower end of one side of the Y-connector is connected to a primary separator and an electric submersible pump unit in sequence, and the other side is connected to a return oil pipe; the upper part of the Y-connector is provided with a locking groove, a positioning step and a sealing surface; The retrieval-capable secondary cyclone separator is located inside the Y-joint and is locked to the Y-joint via its locking mechanism.

[0014] Furthermore, the Y-connector is internally provided with a reinjection channel after separation and a confluence channel for primary and secondary oil extraction.

[0015] Furthermore, the primary separator includes a primary separator core and a primary oil extraction pipe disposed on the upper part of the primary separator core.

[0016] Furthermore, the bridge-type channel is disposed between the positioning seal and the Y-joint to guide the low-oil-content wastewater from the reinjection pipe to the water injection layer.

[0017] Thirdly, the present invention provides a method for downhole oil-water separation using the above-described process string, comprising the following steps: Start the electric submersible pump unit. The produced fluid enters the casing annulus through the central oil pipe and is separated by cyclone separation through the primary separator. The separated oil-rich produced fluid is lifted to the ground through the lift oil pipe, and the low-oil-content wastewater is reinjected to the water injection layer through the reinjection channel of the Y joint and the reinjection oil pipe. Furthermore, when the water content of the produced liquid increases, the secondary hydrocyclone separator described in any one of claims 1 to 4 is lowered through the lifting oil pipe to the positioning step of the Y-joint, so that the secondary hydrocyclone core can perform secondary separation on the reinjected water after the primary separation. The separated oil-rich produced liquid enters the secondary oil intake pipe, and after merging with the primary oil intake pipe through the flow control nozzle, it is lifted to the ground through the lifting oil pipe. The low-oil-content wastewater after secondary separation is reinjected to the water injection layer through the reinjection oil pipe and the bridge channel.

[0018] This invention provides a deployable two-stage cyclone separator, comprising, from bottom to top, a locking mechanism, a flow control nozzle, a two-stage oil extraction pipe, and a two-stage cyclone core. The locking mechanism has a limiting structure for locking with a downhole Y-connector. The flow control nozzle is used to adjust the oil collection ratio between the first-stage and second-stage oil extraction stages to optimize the two-stage separation effect. The two-stage cyclone core is used to perform secondary cyclone separation on the reinjected water after the first-stage separation. The separated oil-rich product fluid enters the two-stage oil extraction pipe. Through the cooperation of the locking mechanism, the flow control nozzle, the two-stage oil extraction pipe, and the two-stage cyclone core, the collection ratio of the two-stage separator can be adjusted, allowing the two-stage separator to operate under optimal conditions. This ensures the long-term effective and reliable operation of the downhole separation system even when the downhole product fluid properties change or the injection and production parameters are adjusted.

[0019] The process tubing provided by this invention employs a deployable two-stage cyclone separator, which allows for adjustment of separator parameters according to different operating conditions, thereby improving the separation effect and solving problems such as low separation efficiency, high requirements for the physical properties of produced oil, and stringent well selection conditions associated with single-stage cyclone separators. At the same time, it avoids the problem of directly using multi-stage separators in series, which increases the complexity of the system and adds difficulty and risk to oilfield operations, especially offshore oilfield operations.

[0020] The downhole oil-water separation method provided by this invention involves two-stage separation of oil-rich produced fluids, which are then combined through flow control nozzles and lifted to the surface via an upper lifting tubing. After further separation, low-oil-content wastewater is reinjected into the water injection layer through reinjection tubing and a lower bridge-type channel. This further reduces the oil content in the reinjected water, improves separation efficiency, and ensures long-term effective and reliable operation of the downhole separation system despite changes in the physical properties of the produced fluids and adjustments to injection and production parameters. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the downhole oil-water separation process tubing of the present invention; Figure 2 This is a schematic diagram of an embodiment of the two-stage hydrocyclone separator capable of being retrieved according to the present invention.

[0023] In the diagram: A. Reinjection channel after separation; B. Merging channel for primary and secondary oil extraction; 1. Casing; 2. Perforated tubing; 3. Insertion seal; 4. Central tubing; 5. Positioning seal; 6. Bridge channel; 7. Reinjection tubing; 8. Retrievable secondary cyclone separator; 8-1. Secondary cyclone core; 8-2. Secondary oil extraction tubing; 8-3. Check valve; 8-4. Flow control nozzle; 8-5. Locking mechanism; 9. Special Y-joint; 10. ESP unit; 11. Primary separator; 11-1. Primary separator core; 11-2. Primary oil extractor; 12. Lift tubing; 13. Cable packer; 14. Downhole safety valve; 15. Cable. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] In the description of this invention, it should be understood that the terms "center," "side," "length," "width," "height," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and "side," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Figure 1 This is a structural schematic diagram of this embodiment, as shown below. Figure 1 As shown, this embodiment provides a downhole oil-water separation process string for a deployable two-stage cyclone separator, including an outer casing 1 and a perforated pipe 2, an insertion seal 3, a central tubing 4, a positioning seal 5, a bridge-type channel 6, a Y-joint 9, a lifting tubing 12, a cable packer 13, and a downhole safety valve 14, which are arranged inside the casing 1 and connected sequentially from bottom to top.

[0028] The Y-connector 9 has a primary separator 11 and an electric submersible pump unit 10 connected sequentially to one side of its lower end, and a return oil pipe 7 connected to the other side. The upper part of the Y-connector 9 is provided with a locking groove, a positioning step and a sealing surface.

[0029] To adjust the flow ratio of the two-stage separator and ensure its optimal operation under varying conditions, thereby guaranteeing the long-term effective and reliable operation of the downhole separation system despite changes in the physical properties of the produced fluid and adjustments to injection and production parameters, such as... Figure 2As shown, this embodiment also provides a salvageable secondary cyclone separator 8, which is disposed inside the Y-connector 9 and locked to the Y-connector 9 by its locking mechanism 8-5. The Y-connector 9 is provided with a reinjection channel A after separation and a confluence channel B for primary and secondary oil extraction.

[0030] Specifically, the retrievable secondary cyclone separator 8 includes, from bottom to top, a locking mechanism 8-5, a flow control nozzle 8-4, a secondary oil extraction pipe 8-2, and a secondary cyclone core 8-1. The locking mechanism 8-5 has a limiting structure for locking with the downhole Y-connector 9. In this embodiment, the limiting mechanism includes a locking boss that engages with the locking groove of the Y-connector 9 to prevent rotational locking. Specifically, the limiting mechanism also includes a first positioning step that engages with the second positioning step of the Y-connector 9 for axial positioning. The flow control nozzle 8-4 adjusts the oil collection ratio between the primary and secondary oil extraction stages to optimize the two-stage separation effect. The secondary cyclone core 8-1 performs secondary cyclone separation on the reinjected water after primary separation, with the separated oil-rich product entering the secondary oil extraction pipe 8-2. In this embodiment, the retrievable secondary cyclone separator also includes a one-way valve 8-3, located upstream of the secondary oil extraction pipe 8-2, to prevent backflow of the separated oil-rich product.

[0031] This retrievable two-stage cyclone separator 8 allows for nozzle size replacement at the wellhead. By employing this retrievable two-stage cyclone separator 8 in the downhole oil-water separation process string, the separator parameters can be adjusted according to different operating conditions, improving separation efficiency and solving problems such as low separation efficiency, high requirements for the physical properties of produced oil, and stringent well selection conditions associated with single-stage cyclone separators. Simultaneously, it avoids the increased complexity of the system caused by directly using multi-stage separators in series, which adds difficulty and risk to oilfield operations, especially offshore oilfields.

[0032] In this embodiment, the primary separator 11 includes a primary separator core 11-1 and an upper primary oil intake pipe 11-2. The flow control nozzle 8-4 can regulate the oil collection ratio of the primary oil intake pipe 11-2 and the secondary oil intake pipe 8-2 to optimize the two-stage separation effect. The bridge-type channel 6 is located between the positioning seal 5 and the Y-joint 9, and is used to guide the low-oil-content wastewater from the reinjection pipe 7 to the water injection layer.

[0033] The method for downhole oil-water separation using the above-mentioned process tubing includes the following steps: Start the electric submersible pump unit 10. The produced liquid enters the casing annulus through the central oil pipe 4 and is separated by cyclone separation through the first-stage separator 11. The separated oil-rich produced liquid is lifted to the ground through the lift oil pipe 12. The low-oil-content wastewater is reinjected to the water injection layer through the reinjection channel A of the Y joint 9 and the reinjection oil pipe 7. When the water content of the produced liquid increases, the lifting oil pipe 12 is lowered into the positioning step of the secondary hydrocyclone separator 8 to the Y-joint 9, so that the secondary hydrocyclone core 8-1 performs secondary separation on the reinjected water after the primary separation. The oil-rich produced liquid after separation enters the secondary oil intake pipe 8-2, and after passing through the flow control nozzle 8-4 and merging with the primary oil intake pipe 11-2, it is lifted to the ground through the lifting oil pipe 12. The low-oil-content wastewater after secondary separation is reinjected to the water injection layer through the reinjection oil pipe 7 and the bridge channel 6.

[0034] Specifically, the working principle of this embodiment is as follows: During normal production of the downhole oil-water separation, the electric submersible pump unit 10 is started. The produced fluid passes through the central tubing 4 to the annulus of the casing 1, and after separation by the electric submersible pump unit 10 and the first-stage cyclone separator 11, it is lifted to the surface through the upper lifting tubing 12. The low-oil-content wastewater is reinjected to the water injection layer through the special Y-joint reinjection channel A and the reinjection tubing 7. When the water content of the produced fluid further increases, the separation requirements are higher, so a second-stage separation is needed to improve the separation efficiency. At this time, the second-stage cyclone separator 8 can be lowered through the upper lifting tubing 12 to the positioning step of the special Y-joint 9. Its second-stage cyclone core 8-1 further separates the reinjected water after the first-stage separation. The oil-rich produced fluid after separation enters the channel of the second-stage oil extraction pipe 8-2. The flow control nozzle 8-4 can regulate the oil collection ratio of the first-stage oil extraction port 11-2 and the second-stage oil extraction pipe 8-2 to optimize the two-stage separation effect. After two-stage separation, the oil-rich product is combined through flow control nozzles 8-4 and then lifted to the ground through the upper lifting oil pipe 12. The low-oil-content wastewater after further separation is reinjected into the water injection layer through the reinjection oil pipe 7 and the lower bridge-type channel 6, thereby further reducing the oil content in the reinjected water and improving the separation efficiency.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A two-stage hydrocyclone separator capable of being used for retrieval, characterized in that: Including settings from bottom to top: The locking mechanism (8-5) is provided with a limiting structure for locking with the downhole Y-connector (9); Flow control nozzle (8-4), the flow control nozzle (8-4) is used to adjust the oil collection ratio of primary oil extraction and secondary oil extraction; Secondary oil intake pipe (8-2); The secondary cyclone core (8-1) is used to perform secondary cyclone separation on the reinjection water after primary separation, and the separated oil-rich product enters the secondary oil extraction pipe (8-2).

2. The two-stage hydrocyclone separator capable of being retrieved according to claim 1, characterized in that: It also includes a check valve (8-3), which is located upstream of the secondary oil intake pipe (8-2).

3. The two-stage hydrocyclone separator capable of being retrieved according to claim 1, characterized in that: The limiting mechanism includes a locking boss, which is used to engage with the locking groove of the Y connector (9).

4. The two-stage hydrocyclone separator capable of being retrieved according to claim 3, characterized in that: The limiting mechanism further includes a first positioning step, which is used to engage with the second positioning step of the Y connector (9) for locking.

5. A downhole oil-water separation process string, characterized in that, Includes the drop-and-retrieve secondary cyclone separator (8) as described in any one of claims 1-4, an outer casing (1), and a perforated pipe (2), an insertion seal (3), a central tubing (4), a positioning seal (5), a bridge channel (6), a Y-joint (9), a lifting tubing (12), a cable packer (13), and a downhole safety valve (14) arranged inside the casing (1) and connected sequentially from bottom to top, wherein: The lower end of one side of the Y-connector (9) is connected to a primary separator (11) and an electric submersible pump unit (10) in sequence, and the other side is connected to a return oil pipe (7); the upper part of the Y-connector (9) is provided with a locking groove, a positioning step and a sealing surface; The scoopable secondary cyclone separator (8) is located inside the Y connector (9) and is locked to the Y connector (9) by its locking mechanism (8-5).

6. The downhole oil-water separation process string according to claim 5, characterized in that: The Y-connector (9) is provided with a reinjection channel (A) after separation and a confluence channel (B) for primary and secondary oil extraction.

7. The downhole oil-water separation process string according to claim 5, characterized in that: The primary separator (11) includes a primary separator core (11-1) and a primary oil intake pipe (11-2) disposed on the upper part of the primary separator core (11-1).

8. The downhole oil-water separation process string according to claim 5, characterized in that: The bridge channel (6) is located between the positioning seal (5) and the Y joint (9) to guide the low-oil-content sewage from the reinjection pipe (7) to the water injection layer.

9. A method for downhole oil-water separation using the downhole oil-water separation process string according to any one of claims 5 to 8, characterized in that, Includes the following steps: Start the electric submersible pump unit (10), and the produced liquid enters the casing annulus through the central oil pipe (4). It is separated by cyclone separation through the first-stage separator (11). The separated oil-rich produced liquid is lifted to the ground through the lifting oil pipe (12), and the low-oil-content wastewater is reinjected to the water injection layer through the reinjection channel (A) of the Y joint (9) and the reinjection oil pipe (7).

10. The downhole oil-water separation method according to claim 9, characterized in that, Also includes: When the water content of the produced liquid increases, the secondary cyclone separator (8) is lowered into the positioning step of the Y connector (9) through the lifting oil pipe (12), so that the secondary cyclone core (8-1) can perform secondary separation on the reinjection water after the primary separation. The oil-rich produced liquid after separation enters the secondary oil intake pipe (8-2), and after being merged with the primary oil intake pipe (11-2) through the flow control nozzle (8-4), it is lifted to the ground through the lifting oil pipe (12). The low oil content wastewater after secondary separation is reinjected to the water injection layer through the reinjection oil pipe (7) and the bridge channel (6).

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